kernel/time/itimer.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 1992 Darren Senn
   4  */
   5
   6 /* These are all the functions necessary to implement itimers */
   7
   8 #include <linux/mm.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/syscalls.h>
  11 #include <linux/time.h>
  12 #include <linux/sched/signal.h>
  13 #include <linux/sched/cputime.h>
  14 #include <linux/posix-timers.h>
  15 #include <linux/hrtimer.h>
  16 #include <trace/events/timer.h>
  17 #include <linux/compat.h>
  18
  19 #include <linux/uaccess.h>
  20
  21 /**
  22  * itimer_get_remtime - get remaining time for the timer
  23  *
  24  * @timer: the timer to read
  25  *
  26  * Returns the delta between the expiry time and now, which can be
  27  * less than zero or 1usec for an pending expired timer
  28  */
  29 static struct timespec64 itimer_get_remtime(struct hrtimer *timer)
  30 {
  31         ktime_t rem = __hrtimer_get_remaining(timer, true);
  32
  33         /*
  34          * Racy but safe: if the itimer expires after the above
  35          * hrtimer_get_remtime() call but before this condition
  36          * then we return 0 - which is correct.
  37          */
  38         if (hrtimer_active(timer)) {
  39                 if (rem <= 0)
  40                         rem = NSEC_PER_USEC;
  41         } else
  42                 rem = 0;
  43
  44         return ktime_to_timespec64(rem);
  45 }
  46
  47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
  48                            struct itimerspec64 *const value)
  49 {
  50         u64 val, interval;
  51         struct cpu_itimer *it = &tsk->signal->it[clock_id];
  52
  53         spin_lock_irq(&tsk->sighand->siglock);
  54
  55         val = it->expires;
  56         interval = it->incr;
  57         if (val) {
  58                 u64 t, samples[CPUCLOCK_MAX];
  59
  60                 thread_group_sample_cputime(tsk, samples);
  61                 t = samples[clock_id];
  62
  63                 if (val < t)
  64                         /* about to fire */
  65                         val = TICK_NSEC;
  66                 else
  67                         val -= t;
  68         }
  69
  70         spin_unlock_irq(&tsk->sighand->siglock);
  71
  72         value->it_value = ns_to_timespec64(val);
  73         value->it_interval = ns_to_timespec64(interval);
  74 }
  75
  76 static int do_getitimer(int which, struct itimerspec64 *value)
  77 {
  78         struct task_struct *tsk = current;
  79
  80         switch (which) {
  81         case ITIMER_REAL:
  82                 spin_lock_irq(&tsk->sighand->siglock);
  83                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  84                 value->it_interval =
  85                         ktime_to_timespec64(tsk->signal->it_real_incr);
  86                 spin_unlock_irq(&tsk->sighand->siglock);
  87                 break;
  88         case ITIMER_VIRTUAL:
  89                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
  90                 break;
  91         case ITIMER_PROF:
  92                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
  93                 break;
  94         default:
  95                 return(-EINVAL);
  96         }
  97         return 0;
  98 }
  99
 100 static int put_itimerval(struct __kernel_old_itimerval __user *o,
 101                          const struct itimerspec64 *i)
 102 {
 103         struct __kernel_old_itimerval v;
 104
 105         v.it_interval.tv_sec = i->it_interval.tv_sec;
 106         v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
 107         v.it_value.tv_sec = i->it_value.tv_sec;
 108         v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
 109         return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0;
 110 }
 111
 112
 113 SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value)
 114 {
 115         struct itimerspec64 get_buffer;
 116         int error = do_getitimer(which, &get_buffer);
 117
 118         if (!error && put_itimerval(value, &get_buffer))
 119                 error = -EFAULT;
 120         return error;
 121 }
 122
 123 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
 124 struct old_itimerval32 {
 125         struct old_timeval32    it_interval;
 126         struct old_timeval32    it_value;
 127 };
 128
 129 static int put_old_itimerval32(struct old_itimerval32 __user *o,
 130                                const struct itimerspec64 *i)
 131 {
 132         struct old_itimerval32 v32;
 133
 134         v32.it_interval.tv_sec = i->it_interval.tv_sec;
 135         v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
 136         v32.it_value.tv_sec = i->it_value.tv_sec;
 137         v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
 138         return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0;
 139 }
 140
 141 COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
 142                        struct old_itimerval32 __user *, value)
 143 {
 144         struct itimerspec64 get_buffer;
 145         int error = do_getitimer(which, &get_buffer);
 146
 147         if (!error && put_old_itimerval32(value, &get_buffer))
 148                 error = -EFAULT;
 149         return error;
 150 }
 151 #endif
 152
 153 /*
 154  * The timer is automagically restarted, when interval != 0
 155  */
 156 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 157 {
 158         struct signal_struct *sig =
 159                 container_of(timer, struct signal_struct, real_timer);
 160         struct pid *leader_pid = sig->pids[PIDTYPE_TGID];
 161
 162         trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
 163         kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);
 164
 165         return HRTIMER_NORESTART;
 166 }
 167
 168 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 169                            const struct itimerspec64 *const value,
 170                            struct itimerspec64 *const ovalue)
 171 {
 172         u64 oval, nval, ointerval, ninterval;
 173         struct cpu_itimer *it = &tsk->signal->it[clock_id];
 174
 175         nval = timespec64_to_ns(&value->it_value);
 176         ninterval = timespec64_to_ns(&value->it_interval);
 177
 178         spin_lock_irq(&tsk->sighand->siglock);
 179
 180         oval = it->expires;
 181         ointerval = it->incr;
 182         if (oval || nval) {
 183                 if (nval > 0)
 184                         nval += TICK_NSEC;
 185                 set_process_cpu_timer(tsk, clock_id, &nval, &oval);
 186         }
 187         it->expires = nval;
 188         it->incr = ninterval;
 189         trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
 190                            ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 191
 192         spin_unlock_irq(&tsk->sighand->siglock);
 193
 194         if (ovalue) {
 195                 ovalue->it_value = ns_to_timespec64(oval);
 196                 ovalue->it_interval = ns_to_timespec64(ointerval);
 197         }
 198 }
 199
 200 /*
 201  * Returns true if the timeval is in canonical form
 202  */
 203 #define timeval_valid(t) \
 204         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 205
 206 static int do_setitimer(int which, struct itimerspec64 *value,
 207                         struct itimerspec64 *ovalue)
 208 {
 209         struct task_struct *tsk = current;
 210         struct hrtimer *timer;
 211         ktime_t expires;
 212
 213         switch (which) {
 214         case ITIMER_REAL:
 215 again:
 216                 spin_lock_irq(&tsk->sighand->siglock);
 217                 timer = &tsk->signal->real_timer;
 218                 if (ovalue) {
 219                         ovalue->it_value = itimer_get_remtime(timer);
 220                         ovalue->it_interval
 221                                 = ktime_to_timespec64(tsk->signal->it_real_incr);
 222                 }
 223                 /* We are sharing ->siglock with it_real_fn() */
 224                 if (hrtimer_try_to_cancel(timer) < 0) {
 225                         spin_unlock_irq(&tsk->sighand->siglock);
 226                         hrtimer_cancel_wait_running(timer);
 227                         goto again;
 228                 }
 229                 expires = timespec64_to_ktime(value->it_value);
 230                 if (expires != 0) {
 231                         tsk->signal->it_real_incr =
 232                                 timespec64_to_ktime(value->it_interval);
 233                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 234                 } else
 235                         tsk->signal->it_real_incr = 0;
 236
 237                 trace_itimer_state(ITIMER_REAL, value, 0);
 238                 spin_unlock_irq(&tsk->sighand->siglock);
 239                 break;
 240         case ITIMER_VIRTUAL:
 241                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
 242                 break;
 243         case ITIMER_PROF:
 244                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
 245                 break;
 246         default:
 247                 return -EINVAL;
 248         }
 249         return 0;
 250 }
 251
 252 #ifdef CONFIG_SECURITY_SELINUX
 253 void clear_itimer(void)
 254 {
 255         struct itimerspec64 v = {};
 256         int i;
 257
 258         for (i = 0; i < 3; i++)
 259                 do_setitimer(i, &v, NULL);
 260 }
 261 #endif
 262
 263 #ifdef __ARCH_WANT_SYS_ALARM
 264
 265 /**
 266  * alarm_setitimer - set alarm in seconds
 267  *
 268  * @seconds:    number of seconds until alarm
 269  *              0 disables the alarm
 270  *
 271  * Returns the remaining time in seconds of a pending timer or 0 when
 272  * the timer is not active.
 273  *
 274  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 275  * negative timeval settings which would cause immediate expiry.
 276  */
 277 static unsigned int alarm_setitimer(unsigned int seconds)
 278 {
 279         struct itimerspec64 it_new, it_old;
 280
 281 #if BITS_PER_LONG < 64
 282         if (seconds > INT_MAX)
 283                 seconds = INT_MAX;
 284 #endif
 285         it_new.it_value.tv_sec = seconds;
 286         it_new.it_value.tv_nsec = 0;
 287         it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0;
 288
 289         do_setitimer(ITIMER_REAL, &it_new, &it_old);
 290
 291         /*
 292          * We can't return 0 if we have an alarm pending ...  And we'd
 293          * better return too much than too little anyway
 294          */
 295         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) ||
 296               it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
 297                 it_old.it_value.tv_sec++;
 298
 299         return it_old.it_value.tv_sec;
 300 }
 301
 302 /*
 303  * For backwards compatibility?  This can be done in libc so Alpha
 304  * and all newer ports shouldn't need it.
 305  */
 306 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
 307 {
 308         return alarm_setitimer(seconds);
 309 }
 310
 311 #endif
 312
 313 static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
 314 {
 315         struct __kernel_old_itimerval v;
 316
 317         if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval)))
 318                 return -EFAULT;
 319
 320         /* Validate the timevals in value. */
 321         if (!timeval_valid(&v.it_value) ||
 322             !timeval_valid(&v.it_interval))
 323                 return -EINVAL;
 324
 325         o->it_interval.tv_sec = v.it_interval.tv_sec;
 326         o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
 327         o->it_value.tv_sec = v.it_value.tv_sec;
 328         o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
 329         return 0;
 330 }
 331
 332 SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
 333                 struct __kernel_old_itimerval __user *, ovalue)
 334 {
 335         struct itimerspec64 set_buffer, get_buffer;
 336         int error;
 337
 338         if (value) {
 339                 error = get_itimerval(&set_buffer, value);
 340                 if (error)
 341                         return error;
 342         } else {
 343                 memset(&set_buffer, 0, sizeof(set_buffer));
 344                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 345                             " Misfeature support will be removed\n",
 346                             current->comm);
 347         }
 348
 349         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 350         if (error || !ovalue)
 351                 return error;
 352
 353         if (put_itimerval(ovalue, &get_buffer))
 354                 return -EFAULT;
 355         return 0;
 356 }
 357
 358 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
 359 static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
 360 {
 361         struct old_itimerval32 v32;
 362
 363         if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
 364                 return -EFAULT;
 365
 366         /* Validate the timevals in value.  */
 367         if (!timeval_valid(&v32.it_value) ||
 368             !timeval_valid(&v32.it_interval))
 369                 return -EINVAL;
 370
 371         o->it_interval.tv_sec = v32.it_interval.tv_sec;
 372         o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
 373         o->it_value.tv_sec = v32.it_value.tv_sec;
 374         o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
 375         return 0;
 376 }
 377
 378 COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
 379                        struct old_itimerval32 __user *, value,
 380                        struct old_itimerval32 __user *, ovalue)
 381 {
 382         struct itimerspec64 set_buffer, get_buffer;
 383         int error;
 384
 385         if (value) {
 386                 error = get_old_itimerval32(&set_buffer, value);
 387                 if (error)
 388                         return error;
 389         } else {
 390                 memset(&set_buffer, 0, sizeof(set_buffer));
 391                 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
 392                             " Misfeature support will be removed\n",
 393                             current->comm);
 394         }
 395
 396         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 397         if (error || !ovalue)
 398                 return error;
 399         if (put_old_itimerval32(ovalue, &get_buffer))
 400                 return -EFAULT;
 401         return 0;
 402 }
 403 #endif